This project will determine the performance and operating specifications for a low-cost optical ammonia sensor for medical applications. Ammonia in human breath has been established as a significant biomarker with high potential for treating kidney and liver diseases as well as detection of bacterial infections. Widespread application of breath tests is currently hampered by the lack of availability of small, portable, cost- effective, highly accurate and reliable sensors. This new sensor will address this need. It will allow the detection of ammonia in untreated breath at medically relevant concentrations ranging from 10 parts-per-billion to 10 parts-per-million. The proposed ammonia breath analyzer combines DPSS lasers with ultra-sensitive photoacoustic spectroscopy operating in a compact and simple analysis cell. This combination provides a unique tool for ammonia detection that is user friendly with a moderate price point. The proposed instrumentation platform shall allow widespread distribution of ammonia breath testing. PUBLIC HEALTH RELEVANCE: The development of a high performance respiratory analyzer for detecting the critical breath component ammonia is proposed. The analyzer is suited for broad noninvasive screening for incipient kidney failure, kidney function monitoring in at- risk populations, treatment of kidney diseases, management of liver cirrhosis, detection of H. pylori infection as well as applications in sports medicine. [unreadable] [unreadable] [unreadable]